My secret chert

If you walk up in Mountain View Cemetery you’ll see all sorts of exotic stone. Nowadays fine stone is a worldwide product. There’s a fabulous anorthosite you’ll see sometimes that comes from Scandinavia. Rapakivi granite too. But I think the older stones include marble possibly quarried across the bay—across the San Andreas fault, actually. Some of the old granite undoubtedly comes from California, whether the Sierra Nevada or the Salinian block in Monterey County. I enjoy all those. But here and there you’ll see stonework incorporating the local stuff, chert and calc-silicate from the Piedmont hill, part of the Novato Quarry terrane in the Franciscan complex. And even more charming is the occasional outcrop, left wild, like this dignified chert.

3 Responses to “My secret chert”

what’s cool about these cherts is that they are analogous to the cherts of the Ouachita mountains in Arkansas (also the Marathon and Davis complexes in Texas), in that they are a radiolarian cherts tectonically pushed up onto the continent and made famous as sharpening (whet) stones, on the down side, the cherts of the Franciscan complex are often out of a green or blueschist facies and too altered to be abrasive (too recrystalized)

Yeah, Oakland’s cherts are good for nothing. They make picturesque knockers. If I ever win the lottery I want to poke around Arkansas and the Texas outliers. But my local cherts are lovely stones. I keep finding them as I dig in the yard and putting them in a pile.

In a cemetery, headstones of local stone may indicate that a family was not affluent enough to buy exotic stone. (I guess if local stone is fabulous [cemeteries in Vermont?], then this rule of thumb does not apply.) This gives me a feeling of having a teasing view into a moment in history of a family, and perhaps of a community.